Synchronous-machine starting devices for starting synchronous machines such as electric generator and electric motor have been developed. Conventionally, the synchronous-machine starting device uses a mechanical distributor for detecting the position of a rotor of a synchronous machine by means of a proximity switch or the like. The mechanical distributor, however, is liable to be broken and influenced by noise due to many wires.
An example of the synchronous-machine starting device for eliminating the need for such a mechanical distributor is disclosed in Japanese Patent Laying-Open No. 2006-271038 (Patent Document 1). Specifically, this synchronous-generator starting device includes an externally communicated converter formed of externally communicated devices such as thyristors, and an externally communicated inverter formed of externally communicated devices such as thyristors for converting DC (direct current) power obtained by the converter into AC (alternating current) power, and starts a synchronous generator receiving AC power obtained by the inverter. The synchronous-generator starting device includes an AC voltage detector for detecting a voltage of an armature terminal of the synchronous generator, an AC current detector for detecting an inverter output current flown from the inverter to an armature of the synchronous generator, an induction voltage operating circuit calculating, from the detected value of the inverter AC current from the output current detector and from a first estimated value of the synchronous generator's rotational speed, an in-phase component and an orthogonal component, relative to a first reference phase, of an induction voltage induced to an armature winding of the synchronous generator by a field current of the synchronous generator, and a PLL circuit outputting a second reference phase and a second estimated value of the synchronous generator's rotational speed that cause the orthogonal component of the first reference phase of the induction voltage from the induction voltage operating circuit to be zero. This synchronous-generator starting device generates a gate pulse of the inverter of a predetermined control advance angle, based on the second reference phase that is output from the PLL circuit, and applies the second reference phase to the first reference phase of the induction voltage operating circuit, and applies the second estimated value of the synchronous generator's rotational speed to the first estimated value of the synchronous generator's rotational speed of the induction voltage operating circuit.    Patent Document 1: Japanese Patent Laying-Open No. 2006-271038